Load transfer device



April 21, 1959 c, YEQMAN 2,882,804

LOAD TRANSFER DEVICE Filed' Feb. 1a. 1954 IN VEN TOR.

Pay C r: yeah BY 7 United States Patent LOAD TRANSFER DEVICE Ray CyrusYeoman, Lufkin, Tex., assignor to Texas Foundries, Inc., Lufkin, Tex., acorporation of Texas Application February 18, 1954, Serial No. 411,180

4 Claims. (Cl. 94-8) This invention relates to a load transfer device ofthe type described in my earlier issued Patents No. 2,261,602 and No.2,355,771. It relates more particularly to improvements in load transferdevices of the type described for interconnecting adjacent slabs ofconcrete in a manner to equalize the forces existing during manufactureand use and to reinforce the edge portions of the concrete slabs.

This and other objects and advantages of this invention will hereinafterappear and for purposes of illustration, but not of limitation,embodiments of the invention are shown in the accompanying drawings inwhich-- Figure 1 is an elevational view of a load transfer deviceembodying features of this invention in position of use in roadconstruction;

Figure 2 is a perspective view showing the separated elements of theload transfer device of Figure l, and

Figure 3 is a top plan view of the assembly shown in position of use inFigure 1.

The improvements embodying features of this invention will be describedin a load transfer device used in bridging the space 11 that is usuallyprovided to enable expansion and contraction between two concrete slabs12 and 13 laid in end to end relation upon a subgrade 14 to form a roadbed in the form of a substantially endless strip of concrete. The spacebetween the slabs is usually filled with a filler 15 such as a woodboard capable of expansion and contraction in response to movement ofthe slabs for maintaining a sealing relation therebetween and asphalt 16or other water-repellent material capable of plastic flow is provided atthe upper end portion to minimize infiltration of free water, dirt orother foreign substance which might otherwise interfere with the normaloperation of the assembly.

Anchored to the board filler 15 in laterally spaced apart relation,preferably in the area intermediate the top and bottom edges, are aplurality of load transfer devices 10 each of which is formed of a pairof substantially identical metal parts A and B formed of corrosionresisting metal, such as by casting of malleable iron or the like. Theelements A and B are substantially identical in shape, each including abody portion 17 of rectangular cross section having a greater lengththan width and with a rectangular recess 18 of smaller dimension formedin one face thereof extending to the inner edge with walls 19, 20 and 21all around the outer three edges.

Integral with the body portion 18 and extending curvilinearly rearwardlyfrom the upper edge thereof is a tension arm 22 having a number of ribs23 spaced through the length thereof for reinforcement and to enhancethe anchorage relation of the arm and the body portion to which it isattached in the concrete. The tension arm is also formed preferably witha downwardly turned end portion 24 to provide a gripping relation whichfunctions somewhat as the root of a tree to anchor the tension arm intothe concrete slab into which it extends substantially to form anintegral part thereof.

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Integral also with the body portion 17 is a compression arm 25 whichextends rearwardly from the lower portion of the end wall and which isprovided with a button 26 on the end of the arm to achieve a desiredbonding and anchoring relation between the compression arm and the bodyof concrete into which it extends. Instead of forming the compressionarm as a member which extends rearwardly from the end wall as described,the compression member may be formed as a curvilinear arm, similar tothat of the tension arm previously described but in which the endportion extends upwardly to pro vide the desired anchoring relation andin which the arm extends rearwardly from the lower wall of the bodyportion.

Integral with the body portion 17 and extending forwardly from theforward edge thereof defined by the recessed portion and flush with theinner face thereof is a cantilever bridging plate or arm 29 ofcorresponding shape but of slightly lesser width and thickness than therecess 18 in the body portion so that the cantilever bridging arm of oneof the elements will be received in the recess of the other with slightclearance between the side walls. Except for the clearance, the purposeof which will hereinafter be described, the elements respond generallyto the constructions which have heretofore been used in load transferdevices as defined in the patents previously mentioned.

The parts are interconnected in an assembled relation with the twosubstantially identical castings being joined in face to face relationwith the cantilever bridging arm 29 of one being received in the recess18 of the other with a spaced relation between the inner ends of thebody portions providing a groove 30 dimensioned to correspond to thethickness of the filler strip 15 to enable a mounting relation to beeffected on the strip through notches provided therein. The assembledrelation is maintained by a bolt 31 and nut 32 or other similar joiningmeans operating through an opening 33 in an intermediate portion of thecantilever bridging arm and adjacent its rearward edge and the openingin one is in registry with the similarly located opening in thecantilever bridging arm of the other when in properly assembledrelation. Each of the openings are formed with an exterior and aninterior chamfer 34 and 35 respectively with an intermediate constrictedportion 36 therebetween dimensioned to be sufficiently larger than thearea of the bolt member extending therethrough to enable angularmovement. The outside chamfer 34 is dimensioned to receive the nut 32 orthe head of the bolt 31 so as to be substantially completely concealedtherein thereby to avoid interference with the positioning of theassembled device within a notch dimensioned to receive the assembledload transfer device in fitting relation and in a manner to enable freemovement of the cantilever bridging arm in and out of the surroundingconcrete pocket when excessive expansion of the concrete takes place.

During cure and immediately thereafter, it has been found that theconcrete is incapable of development of maximum strength propertiessufficient to resist being broken up in the event that substantialforces are developed. As a result, it is essential to provide means topermit relative movement between the parts of the load transfer deviceby an amount corresponding to the contractions which might take placeduring the initial stages of the setting of the concrete until such timeas the concrete slab possesses suflicient strength to cause shearing ofthe bolt securing the parts together without deterioration. For suchpurpose, relative movement in amounts up to about inch is sufficient andsuch extended movement can be made available without interfering withthe assembled relation by proper chamfer and dimensioning of thecontricted portion as heretofore described to permit angular adjustmentof the bolt during the setting process.

In use, a compression block 37 is located in the recess between the endof the cantilever arm 29 and the end of the recess in which it isreceived. It is preferred to locate the compression block in advance inthe assembly and for thispurpose, the end wall of the cantileverbridging arm is beveled inwardly from the outer edge as indicated by thenumeral 38 to introduce action which cams the block inwardly against thecooperating wall of the companion part and to prevent outwarddisplacement of the compression block 37 while in the assembled relationthereby to prevent loss or displacement. Loss of the compression blockwhich frequently occurs when the cantilever bridging arm is formedwithout a bevel of thetype described renders the unit inoperativebecause the recess would otherwise become filled with concrete and thenecessary relative movement between the parts of the load transferdevice would be resisted. It is preferred to make use of a compressionblock formed of a material similar to that of the separating strip andof corresponding thickness to provide a balance between the forcesexisting in response to deformation of the compression block and thefiller strips during expansion and contraction of the interconnectedslabs of concrete.

In addition, use is made of a thin strip 39 of a compressible material,such as a pad of paper or other cellulosic sheet, dimensioned to linethe area between the adjacent surfaces of the cantilever bridging armsand the recesses in which they are received to form a separatortherebetween which enables relative movement be tween surfaces withoutinterference because of surface roughness as occasioned in manufactureor by deterioration of the surface subsequent thereto. Without suchseparator, the surface roughness might otherwise freeze the parts toprevent relative movement. When used for this purpose, it is preferredto form the separating liner with a lubricant applied to the surfacesthereof or embodied therein to provide for lubricated movement inoperation.

In addition to the use of the oiled pad to enhance sliding movementbetween the parts, the pad may be fabricated to embody a water repellentand a rust inhibitor to resist infiltration of moisture between theparts which might introduce obstructing forces and the like and whichaids in the resistance to deterioration of the metal by elementsexisting in contact therewith particularly in this critical area whereinthe forces are transmitted from i one part to another while enablingrelative movement.

The oiled pad is preferably dimensioned to have an edge portion 40extending perpendicularly into the space between the lower edge of thecantilever bridging arm and the recess in which it is received to takeup the space between such surfaces and to force metal to metal contactbetween the upper edge of the cantilever bridging arm and the bodyportion to the extent that little, if any, clearance is present whichmight require being taken up before load transmission can take place. Asa result, load transmission will occur practically instantaneously, yetit is preferred that the insert be formed of a compressible materialsufficient to permit a hinged action in response to warping of the partswithout interfering with the operation thereof and further to minimizethe tendency for corrosive freezing which. might otherwise preventrelative movement between the parts.

An important feature of this invention resides in the means embodied ina device of the type described for effecting more desirable alignment ofthe elements with he filler strip by way of longitudinal alignment ofthe load transfer elements with the interconnected slabs of concrete andthe development of a larger and greater bearing between the loadtransfer device and filler for 4 maintaining a more desirableperpendicular relationship between the device and the filler strip.

Another feature resulting from the response which will hereinafter bedescribed resides in the more effective bearing relationship between theconcrete and the elements of the load transfer device at a point wherevertical loads develop the greatest stress in the concrete thereby toimprove the function of the load transfer device in the use for which itis intended.

For this purpose, the body portion of each of the malleable steelcastings is formed with lugs 42 and 43 extending horizontally outwardlyfrom the side walls at the upper and lower forward edge portions of thebody portion with the front faces of the lugs formed flat andsubstantially perpendicular to the length of the body portion and acantilever arm extending forwardly thereof for proper alignment of theelements upon engagement with the filler strip therebetween. Theremainder of the lugs 42 and 43 may be formed to various contours but itis preferred to taper the lugs rearwardly in the body portion in theform of an angular member. The upper and lower surfaces extendingoutwardly into the concrete, when in use, are preferably formed flat tofunction as shelves which add tov the anchorage of the load transferdevice in the concrete and are located at a point for more effectiveacceptance of vertical loads in the concrete where such vertical loadcauses the greatest stress.

Further improvement in the operational characteristics of a loadtransfer device embodying features of this invention results in partfrom the construction wherein the load carrying lug or cantilever arm iscontained firmly within the recess of the companion part which isenclosed on three sides. This enclosure serves a number of importantpurposes. For example, it encloses the working parts of the unit toprovide an improved unitary action and the side enclosures back up thepaper pad in a Way to offer an improved bearing contact between theopposite side of the lug and the body portion of the member in which itis received for instant load transfer. It also serves as a means forincreasing the load carrying capacity of the device after initialdeformation takes place. It will be apparent that when one end of thedevice is loaded tending to cause a hinge action, the enclosed recessbrings into action the companion lug immediately upon compression of thefiller formed of the lubricated cellulosic material. In addition toenclosure of the cantilever bridging memher on three sides, the bridgingmember is also enclosed on its inner surface in a manner to provideefficient location and protection of the arm against unexpectedobstructions and elements with which it might otherwise come in contact.

It will be apparent from the foregoing description that I have provideda number of improvements in load transfer devices of the type heretoforeemployed each of which separately and in combination improves theeificiency and the operation of the device and the assembly andutilization thereof for the purpose for which it was intended. Meansenabling preassembly of the device into its relation for mountingenables the manufacture and assembly of the load transfer elements at acentral location where economies may be practiced in the methods,equipment and processes for manufacture and wherein less inventory willbe required thereby to enable greater efiiciency in manufacture and use.

It will be understood that changes may be made in the details ofconstruction, arrangement and operation of the device without departingfrom the spirit of the invention, especially as defined inthe followingclaims.

I claim:

1. A load transfer device for use in combination with adjacent concreteslabs having a spaced relation therebetween, said device comprising apair of substantially identical but complemental rigid members eachhaving a body portion with. a rectangular recess extendingendwise fromthe inner edge thereof, a cantilever bridging arm of rectangular sectionextending forwardly from the inner edge of the body portion anddisengageably received in slidable bearing relation in the recess of thecomplemental member when in the assembled relation with slight clearancebetween the side edges, a tension arm extending curvilinearly rearwardlyfrom the body portion with means therein for anchorage in the concrete,a compression block positioned in each of the recesses between the endof the bridging arm and the base of the recess, lugs extending laterallyhorizontally from the upper and lower edge portions of the body portionand on opposite sides thereof with the front face of the lugs flush withthe forward edge of the body portion from which the cantilever bridgingarm extends, and means for securing the members together in theassembled relation including a bolt member extending through registeredlateral chamfered openings in said bridging arms, said chamferedopenings being reduced for substantially line contact with said boltmember for permitting rocking movement and tilting action and to permitslight relative endwise movement between the body portions.

2. A load transfer device for use in combination with adjacent concreteslabs having a spaced relation therebetween, said device comprising apair of substantially identical but complemental rigid members eachhaving a body portion with a rectangular recess extending endwise fromthe inner edge thereof, a cantilever bridging arm of rectangular sectionextending forwardly from the inner edge of the body portion anddisengageably received in slidable bearing relation in the recess of thecomplemental member when in the assembled relation with slight clearancebetween the side edges, a tension arm extending curvilinearly rearwardlyfrom the body portion with means therein for anchorage in the concrete,a compression block positioned in each of the recesses between the endof the bridging arm and the base of the recess, and means for securingthe members together in the assembled relation including a bolt memberextending through registered lateral chamfered openings in said bridgingarms, said chamfered openings being reduced for substantially linecontact with said bolt member to permit relative rocking movement,tilting action and slight endwise movement between the body portions.

3. A load transfer device for use in combination with adjacent concreteslabs having a spaced relation therebetween, said device comprising apair of substantially identical but complemental rigid members eachhaving a body portion with a rectangular recess extending endwise fromthe inner edge thereof, a cantilever bridging arm of rectangular sectionextending forwardly from the inner edge of the body portion anddisengageably received in slidable bearing relation in the recess of thecomplemental member when in the assembled relation with slight clearancebetween the side edges, a tension extending curvilinearly rearwardlyfrom the body portion with means therein for anchorage in the concrete,a compression block positioned each of the recesses between the end ofthe bridging arm and the base of the recess, means for securing themembers together in the assembled relation including a bolt memberextending through registered lateral chamfered openings in said bridgingarms, said charnfered openings being reduced for substantially linecontact with said bolt member to permit relative rocking movement,tilting action and slight endwise movement between the body portions,and a compressible strip between the lower surface of the bridging armand the recessed body portion to take up the clearance and to provide abearing contact at the opposite surfiaces between said members for loadtransfer.

4. A load transfer device for use in combination with adjacent concreteslabs having a spaced relation therebetween, said device comprising apair of substantially identical but complemental rigid members eachhaving a body portion with a rectangular recess extending endwise fromthe inner edge thereof, a cantilever bridging arm of rectangular sectionextending forwardly from the inner edge of the body portion anddisengageably received in slidable bearing relation in the recess of thecomplemental member when in the assembled relation with slight clearancebetween the side edges, a tension arm extending curvilinearly rearwardlyfrom the body portion with means therein for anchorage in the concrete,a compression block positioned in each of the recesses between the endof the bridging arm and the base of the recess, and means for securingthe members together in the assembled relation including a :bolt memberextending through registered lateral chamfered openings in said bridgingarms, said chamfered openings being reduced for substantially linecontact with said bolt member to permit relative rocking movement,tilting action and slight endwise movement between the body portions,the cantilever bridging arm having an end which is beveled inwardly fromthe outer edge thereof and is in contact with the compression block tocam the block into the recess when in the assembled relation.

References Cited in the file of this patent UNITED STATES PATENTS2,110,738 Parker Mar. 8, 1938 2,261,602 Yeoman Nov. 4, 1941 2,263,150Westcott Nov. 18, 1941 2,296,756 Yeoman Sept. 22, 1942 2,319,713Williams May 18, 1943 2,608,141 Jacobson Aug. 26, 1952

